Developer composition for lithographic printing plates

ABSTRACT

WHEREIN R1 is a hydrogen atom, an alkyl group, a hydroxy group or a carboxy group; R2 is a hydrogen atom, an alkyl group, a halogen atom, or a carboxyalkyl group; and R3 is a hydrogen atom, a cyano group, a halogen atom or a carboxy group, provided that R2 and R3 may bond together to form a benzene ring.   A developer formulation for silver halide-containing lithographic printing plates which comprises an infectious developer containing hydroquinone as developing agent and, incorporated therein, a compound of the formula:

United States Patent [191 Sakazume et al.

[ DEVELOPER COMPOSITION FOR LITHOGRAPIIIC PRINTING PLATES [73] Assignee: Konishiroku Photo Industry Co.,

Ltd., Tokyo, Japan [22] Filed: Jan. 11, 1973 [21] Appl. No.: 322,875

[30] Foreign Application Priority Data Jan. 17, 1972 Japan 47-6166 [52] US. Cl. 96/66.4, 96/66 R [51] Int. Cl G03c 5/30 [58] Field of Search 96/66, 66.4

[56] 9 References Cited UNITED STATES PATENTS 2,573,027 10/1951 Kendall et al 96/52 2,845,349 7/1958 Schwarz 3,295,981 1/1967 Milton 96/109 [451 Sept. 3, 1974 3,667,954 6/1972 Itano et al 96/90 R Primary ExaminerMary F. Kelley Attorney, Agent, or FirmEric H. Waters [5 7 ABSTRACT A developer formulation for silverhalide-containing lithographic printing plates which comprises an infectious developer containing hydroquinone as developing agent and, incorporated therein, a compound of the formula: W

2 Claims, No Drawings DEVELOPER COMPOSITION FOR LITHOGRAPHIC PRINTING PLATES This invention relates to a developer formulation for silver halide-containing lithographic printing plates which comprises an infectious developer containing hydroquinone as developing agent and, incorporated therein, a compound of the general formula shown below, and aims to overcome the degradation in infectious developability of the infectious developer which is caused by oxidation of the hydroquinone contained therein.

General Formula:

wherein R is a hydrogen atom, an alkyl group, a hydroxy group or a carboxy group; R is a hydrogen atom, on alkyl group, a halogen atom, or a carboxy-alkyl group; and R is a hydrogen atom, a cyano group, a halogen atom or a carboxy group, provided that R and R may bond together to form a benzene ring.

Generally, a lithographic printing master plate bearing a linear or dot image is obtained by developinga lith-type photosensitive material with an infectious developer, which is a hard tone developer. The infectious developer contains hydroquinone as developing agent and, in addition thereto, sodium sulfite and paraformaldehyde. It is considered that the said components bring about such reaction as CH O Na SO H O f CH O NaSO +NaOH to make the developer eitremely low in free sulfite ion concentration. If the infectious developer with the low sulfite concentration is used, the active hydroquinone (semiquinone) in the developer is rather safe from the attack by sulfite ion retaining its active state over a long period of time. Thus, replenishment of activated hydroquinone is possible for a long period, and so the developed image can be made hard in tone. However, the abovementioned infectious developer containing hydroquinone as developing agent which is low in sulfite ion concentration has the disadvantage that the hydroquinone is readily oxidized with lapse of time after preparation of the developer, with the result that the developer is deprived of its infectious developability. The known infectious developer having the abovementioned disadvantage is not satisfactory in practice, and has been required to be improved in storability. In view of the above, facts we made extensive studies and discovered that when a compound of the aforesaid general formula is added to an infectious developer, the hydroquinone contained in the developer is greatly improved in stability to make it possible to prevent the developer from degradation in infectious developability.

It is therefore an object of the present invention to provide an infectious developer formulation containing hydroquinone as developing agent in combination with an addition product of aldehyde and alkali hydrogen sulfite or an addition product of cyclohexane or acetone and a soluble sulfite. That is, the present invention provides an infectious developer composition containing hydroquinone as developing agent in combination with a compound having a carbonyl group C=O) and with a soluble sulfite, to which developer composition has been added the aforesaid compound of the present invention in a proportion of 0.1 to g. per liter of the developer. The compound according to the present invention may be added in a proportion of more than 50 g. per liter of the developer. Even if the compound is added in such a large amount as above, however, the practical effect is not increased as much.

Typical examples of the compound used in the present invention are shown below, but compounds usable in the invention are not limited to these.

1. 3-Hydroxy-6methylpyridazine 3 2. 3-Hydroxypyridazine IOOH 3-Hydroxy-4-cyanopyridazine NO N . 3-Hydroxy-4-cyano-6-methylpyridazine NC N 6. 3-l-lydroxy-4-carboxy-6-methylpyridazine 7. 3,6-Dihydroxypyridazine 1 1. 3,6-Dihydroxy-4-methylpyridazine 8. 3,6-Dihydroxy-4-bromopyridazine n Br N 9. 3,6Dihydroxy-4,5-dibrornopyridazine 10 Br \l/ N A w 10. 3 ,6-Dihydroxy-4-carboxymethylpyr1dazme we- 6..I;.o -2

l HOOCCHz 13 1,4-Diii diox -e-arbdxy-phrh aiiiiine The developer formulation according to the present invention is markedly excellent in preservability and a does not injure the photographic property of the resulting nea qtimaai-m m... n

The present invention is illustrated below with reference to an example.

EXAMPLE A commercially available lithographic film was exposed to light through a gray-scale, and was then developed at 27C. for 2 minutes with each of the developers of the composition shown below immediately after preparation and the same developers as above except that these had been incubated for 24 hours in contact with the air (contact area 28 cm /liter). Thereafter, the sample was subjected to fixing, water-washing and drying treatments and measured in photographic properties to obtain the results as set forth in the table shown below.

Compound Amount Relative Gamma (g/l) speed Immediately after Exemplified preparation 25 1 1.0 compound l) 4 After 24 hours incubation 23 12.0 Immediately after MW Exemplified p paration 24 1 1.5 Developer compound (7) 3 After 24 hours 22 13.0 composition incubation according to the present invention h Immediately after 24 11.0

4 Exemplified 5 preparation compound (11) After 24 hours 21 13.0

incubation g Immediately after 25 1 1.0 Exemplified 3 preparation compound (12) After 24 hours 23 12.5

incubation Immediately after 22 l 1.0 preparation Control No compound After 24 hours l5 8.0 developer added incubation As is clear from the above table, the developer com- What we claim is: 1. A developer composition of low free sulfite concentration for silver halide-containing lithographic printing plates which comprises an infectious developer containing hydroquinone as developing agentand, in-

corporated therein, a compound of the formula,

II R N 2. A developer composition as claimed in claim 1, wherein said compound is selected from the group consisting of 3-hydroxy-6-methylpyridazine, 3,6- dihydroxypyridazine, 3,6-dihydroxy-4- methylpyridazine and 1,4-dihydroxyphthalazine. 

2. A developer composition as claimed in claim 1, wherein said compound is selected from the group consisting of 3-hydroxy-6-methylpyridazine, 3,6-dihydroxypyridazine, 3,6-dihydroxy-4-methylpyridazine and 1,4-dihydroxyphthalazine. 